Flux for welding light alloys

ABSTRACT

Fluxes for welding light alloys such as aluminium or aluminiumbased alloys, composed essentially of the following substances by weight percentage: SODIUM CHLORIDE, 30-35 PERCENT; SODIUM FLUORIDE, 28-30 PERCENT; POTASSIUM CHLORIDE, 15-20 PERCENT; AND LITHIUM FLUORIDE, 20-22 PERCENT. The flux is mostly applicable in machine building for electroslag welding of heavy objects made of light aluminiumbased alloys.

United States Patent Ischenko' et al.

[451 Jan. l8, 1972 FLUX FOR WELDING LIGHT ALLOYS Filed: May 7, 1970 Appl. No; 35,568

Foreign Application Priority Data May 30, 1969 U.S.S.R .J. "1335972 U.S.Cl .....219/l37, 148/26, 219/73 Int. Cl. ..B23k 25/00, 823k 35/36 Field of Search ..148/24, 26', 219/137, 73

References Cited UNITED STATES PATENTS 5/1900 Bates ..148/26 8/1934 Y Binder 148/26 7/1943 Prendergast 148/26 X 5/1951 Miller et al. ..l48/26 8/1957 Stetson et al. 148/26 FOREIGN PATENTS OR APPLICATIONS 231,816 5/1925 GreatBritain ..l48/26 557,725 2/1945 GreatBritain.... ..l48/26 747,813 4/l956 GreatBritain ..l48/26 Primary Examiner- L. Dewayne Rutledge Assistant Examiner-G. T. Olaki Attomey-Holman & Stem [57] ABSTRACT Fluxes for welding light alloys such as aluminium oi aluminium-based alloys, composed essentially of the following substances by weight percentage:

sodium chloride, 30-35 percent;

sodium fluoride, 28-30 percent;

potassium chloride, 15-20 percent; and

lithium fluoride, 20-22 percent.

The flux is mostly applicable in machine building for electroslag welding of heavy objects madeof light aluminiumbased alloys.

2 Claims, No nmviii s FLUX son WELDING LIGHT ALLOYS The present invention relates to fluxes for welding light alloys including those based on aluminum, in heavy items used in machine building.

Classified as light alloys are aluminumand magnesiumbase alloys.

Known heretofore is a flux for welding aluminum-based alloys, its weight percent composition being as follows:

potassium chloride 30-60,

lithium chloride 10-40,

barium chloride -30,

lithium fluoride 2-10 and aluminum fluoride 1.5-6.0

(cf. Author's Certificate of the U.S.S.R. No. 186843).

Said flux, however, is rather costly and proves to be practically water-insoluble which hampers its removal from the weld seam surface.

There is known another flux for welding aluminium-based alloys, its weight percent composition being as follows:

potassium fluoride -40,

sodium fluoride 30-60 and lithium fluoride 20-50 (cf. U.S.S.R. Authors Certificate No. 233422).

Yet such a flux possesses too high a degree of hygroscopicity.

It is an essential object of the present invention to eliminate the above-mentioned disadvantages.

It is a specific object of the present invention to provide a flux for welding light alloys, including aluminium-based ones, featuring such a composition that is of less density when molten than the metal being welded, is instrumental in obtaining a strong and staunch joint when being used in electroslag welding and is cheaper than the conventional fluxes of similar application- Said object is accomplished by the provision of a flux for welding light aluminium-based alloys, comprising potassium chloride and lithium fluoride, of the following weight percent composition, according to the invention:

sodium chloride 30-35,

sodium fluoride 28-30,

potassium chloride -20, and

lithium fluoride -22.

Flux of such a composition features its smelting point and density lower than in aluminum, as well as an optimum.electric conductivity and interfacial tension which ensure a stable proceeding of the electroslag welding process. Said flux is particularly expedient for use in welding aluminium-based alloys where it is conducive in obtaining high-quality welded joints.

For better understanding of the essence of the present invention, given below is an exemplary embodiment thereof.

To prepare the flux disclosed herein the components specified in the present invention are taken, then are dehydrated and weighed in the following weight percent ratio:

sodium chloride 31,

potassium chloride 19,

lithium fluoride 20 and sodium fluoride 30.

Then the components are intermixed and subjected to melting. The melt having been cooled down, it is disintegrated until 1-5 mm. grains are obtained.

The thus-prepared flux has been used experimentally in I electroslag welding of aluminum blocks of busways with 60X430 mm. cross section. 'The resultant welded joint featured a tight and staunch texture and the following mechanical properties:

tensile strength 7.8-8.4 kg./mm.,

weld seam safety factor over 0.95 and angle of bend of specimens 40X60 mm. in cross section-- In another exemplary preparation of the flux according to the invention, its components have been taken in the following weight percent ratio:

sodium chloride 30,

potassium chloride 20, sodium fluoride 28 and lithium fluoride 22.

Similarly to the preceding example the stock components are dried, intermixed and melted, then the melt'is cooled down and disintegrated into grains 1-5 mm. in size.

Electroslag welding with theuse of the thus-obtained flux is efi'ected by the conventional technique.

In thestarting period of the welding process a rapid melting of the flux occurs with the result that an amount of heat is evolved sufficient to melt both the base metal and the electrode metal.

The presence of chlorides in the flux is'conducive to a good wettability of the metal by the flux.

In the course of the welding process a complete separation of the molten metal bath and the slag bath occurs. The presence of the ions of fluorine imparts chemical activity to the flux with respect to oxide films on the surface of the metal being welded, with the result that such oxides are eliminated within the welding zone.

Moreover, slag inclusions are prevented from penetrating into the weld metal, a complete interfusion of the weld metal with the base metal is ensured, and the formation of the welded joint as a whole is improved.

The flux disclosed hereinabove was tested in electroslag welding of aluminum busways with flexible members such as a stack or pile with a 60X430 mm. cross section assembled from lamels 0.8-1 mm. thick each. 7 a

In another case a metal structure 50-250 mm. thick was welded in a single pass vertically at a rate of 5-6 m./hr.

In the above case the welded joint obtained featured its mechanical properties similar to those specified for the former example. 7

Furthermore, the residual flux left in the stack gaps caused no appreciable corrosion for a long period of time after weld- The flux of the composition disclosed above is cheaper, low in hygroscopicity and is readily soluble in water, whereby it is easily removed from the weld seam surface after welding.

What is claimed is:

1. In a method of welding aluminium-based alloys, the improvement comprising using a flux consisting essentially of the following components (in weight percent):

sodium chloride 30-35,

sodium fluoride 28-30,

potassium chloride 15-20, and

lithium fluoride 20-22.

2. A flux for welding light alloys, consisting essentially of the following components (in weight percent):

sodium chloride 30-55,

sodium fluoride 28-30,

potassium chloride 15-20 and lithium fluoride 20-22.

t. l 1 ll 

2. A flux for welding light alloys, consisting essentially of the following components (in weight percent): sodium chloride 30-55, sodium fluoride 28-30, potassium chloride 15-20 and lithium fluoride 20-22. 